Credential manager: Introduce platform interface.

public/platform/WebCredentialManager.h

Index: public/platform/WebCredentialManager.h
diff --git a/public/platform/WebCredentialManager.h b/public/platform/WebCredentialManager.h
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+++ b/public/platform/WebCredentialManager.h
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WebCredentialManager_h
+#define WebCredentialManager_h
+
+#include "public/platform/WebCallbacks.h"
+#include "public/platform/WebCredentialManagerError.h"
+#include "public/platform/WebString.h"
+#include "public/platform/WebVector.h"
+
+namespace blink {
+
+// WebCredentialManager provides an interface for asking Blink's embedder to
+// respond to `navigator.credentials.*` calls.
+class WebCredentialManager {
+public:
+    typedef WebCallbacks<WebCredential, WebCredentialManagerError> RequestCallbacks;
+    typedef WebCallbacks<void, WebCredentialManagerError> NotificationCallbacks;
+
+    WebCredentialManager();
+    virtual ~WebCredentialManager();
+
+    // Ownership of the callback is transferred to the callee for each of the following methods.
+    virtual void dispatchFailedSignIn(const WebCredential&, NotificationCallbacks*) { }
+    virtual void dispatchSignedIn(const WebCredential&, NotificationCallbacks*) { }
+    virtual void dispatchSignedOut(NotificationCallbacks*) { }
+    virtual void dispatchRequest(bool zeroClickOnly, const WebVector<WebString>& federations, RequestCallbacks*) { }
+};
+
+} // namespace blink
+
+#endif // WebCredentialManager_h